When it comes to predicting the weather, no two experts agree. The same apparently holds true in space weather. Nevertheless, a panel of 12 international experts, ranging from solar physicists to modelers, has managed to forge a consensus around the next solar cycle. The prediction: solar minimum—the period of the fewest average number of sunspots and solar storms but the maximum for cosmic rays—will come within six months of March of next year. Cycle 24 will peak in either October 2011 with roughly 140 sunspots that year or in August 2012 with roughly 90 sunspots that year, either slightly above or below the average of 114 sunspots per annum. And this solar cycle will likely last nearly as long as the current one. "Most scientists were expecting the solar cycle to have ended by now," says Douglas Biesecker, physicist at the National Oceanic & Atmospheric Administration's (NOAA) Space Environment Center in Boulder, Colo., and chair of the prediction panel. "We're still a long way from solar minimum."

The sun's behavior is no longer solely a scientific concern; it has impacts ranging from whether astronauts can perform space walks to whether airplanes can fly over polar regions. "Airlines, [global positioning system] and GPS-like users, electric power grid operators, even manned spaceflight are very interested in knowing what space weather is coming and how it will affect them," says Joseph Kunches, chief of the forecast and analysis branch at NOAA's Space Environment Center.

For example, a solar storm in 1989 induced extra current in Hydro Quebec's grid, costing it $30 million. And a cluster of storms around Halloween in 2003 blocked GPS systems that precisely position aircraft over all of North America as well as forced airlines to halt polar flight routes that cut travel time to and from Asia. "If they are not able to have this high-frequency communication, regulations require that they fly at lower latitudes," explains physicist Daniel Baker of the University of Colorado at Boulder. "Generally, this takes the aircraft into stronger headwinds, and it's a longer path. It costs an airline $100,000 or more to change just one flight."

The impacts of space weather can be felt in everything from oil drilling in the Gulf of Mexico (which relies on GPS to precisely place drilling apparatus) to everyday cell phone conversations. As a result, such solar predictions are becoming increasingly valuable and useful. But that doesn't make them any more precise, largely due to disagreements over the internal dynamics of the sun and its sunspots. New observational instruments, such as NASA's Solar Dynamics Observatory, scheduled for launch in August 2008, will allow for a better look inside the sun and therefore a better understanding of its inner workings. Ultimately, that will lead to better predictions. In the meantime, the technologically dependent world can prepare for severe impacts from even moderate solar storms. As Baker says: "Storms don't have to be so super anymore to be causing lots of societal effects as we get more systems that are susceptible."